Flood Control Solutions for Bayou Henderson, Ascension Parish, LA

This paper presents the procedures used to develop a strategy to mitigate flooding in the Bayou Henderson watershed in Ascension Parish, Louisiana. The Bayou Henderson Watershed includes the town of Galvez, Louisiana, and has an area of approximately 3600 hectare. A little more than one-third of the watershed is developed, while the remainder is open or forested areas. The watershed includes agriculture/pastureland, residential, open space and some commercial areas. A map of the Bayou Henderson watershed showing the stream network and land use are provided in Figure 1. The main stem of Bayou Henderson is approximately 10 kilometers in length. It flows southeast until it crosses Henderson Bayou Road. From there, Bayou Henderson flows northeast until it discharges into the Amite River. Bayou Henderson has several major tributaries which drain the urbanized areas in the western part of the watershed. The elevation of the Bayou Henderson channel ranges from about one meter below sea level near its confluence with the Amite River to approximately 6 meters above sea level at the upstream most reaches on the Marty Burratt drainage ditch. The entire Bayou Henderson watershed is located within the Mississippi River 500-year floodplain. In additional, a large area of the Bayou Henderson Watershed is affected by backwater from the Amite River and is included within the Amite River 100-year floodplain. Two types of flooding affect residences and businesses in Henderson Bayou. The first of these is local flooding, which results from heavy rainfall in the immediate drainage area of the Bayou and its tributaries. This type of flooding has worsened in recent years because of increased paved area and floodplain encroachment. The second type of flooding is known as backwater flooding or tailwater flooding. It is caused by flood flow and high water in the Amite River, which then restricts the discharge of Bayou Henderson. These two types of flooding are generally considered to be independent, meaning the underlying causes are not correlated. Therefore, local flooding and backwater flooding can occur individually or jointly from time to time.